DESCRIPTION: High rates of sex trade and drug use, and the intersection of these, exacerbate the spread of HIV in Tijuana, the largest Mexican city bordering the US. Poor socioeconomic conditions are the primary driver of sex work initiation in Tijuana, as well as elsewhere. Previous research by the PI in South Asia has established that economic debt is not only significant in terms of women's initiating sex trade, but is also associated with elevated HIV/STI risk among FSW. Her work indicated that the vast majority of FSW reported informal types of debt (80%) and that this debt reduced women's condom negotiating power with clients, increasing HIV risk. The nature of debt in the US-Mexico border region likely differs significantly from that of South Asia. In Tijuana, high levels of migration as well as widespread drug use likely have an influence on the types of debts women have that may be most influential in increasing HIV risk. Debt may affect women's drug-related HIV risk as well. Based on preliminary interviews with FSW in Tijuana, debts among FSW have been reported in the form of service obligation (e.g. referred to more formally as debt-bondage in other contexts), where women are expected to work in sex work as a way to repay someone who has provided them with money, drugs, or other needs (e.g. costs associated with migration, provision of housing and food). We hypothesize that these informal types of debts and obligation in Tijuana deplete women's agency in sex work, decreasing negotiating power with managers and clients, reducing condom use, increasing GBV victimization and reducing negotiating power during drug use. More work is needed to define the multiple types of debts among FSW in this context and the extent to which these influence HIV risk behaviors. Thus, the proposed study aims: 1) to identify and define the multiple types of debt (including service obligations), and 2) to examine the interrelations between debt, drug use, sex trade, and HIV risk among FSW in Tijuana. To accomplish this, we propose to conduct a mixed-methods study of 400 FSW in Tijuana. Life history interviews with FSW in debt who report drug use (n=25) and non-drug use (n=25) will provide descriptive scenarios related to debt, drug use, and sex work involvement, as well as the implications of these on HIV risk. Quantitative data will also be collected from 400 FSW identified using venue-based sampling, via self-report survey and biologic HIV/STI testing. Findings will inform longitudinal studies to better understand the temporal and interrelated dynamics of debt, drug use, and sex work - and contribution of these to HIV risk among FSW. Findings will also be critical to provide initial direction on debt reduction strategies (e.g. reducing monetary debt as well as to change the social structures that promote debts) to reduce HIV risk among FSW in this region. Such investigation is especially important, given increasing data indicating that promoting economic well-being is an effective HIV prevention strategy among high-risk populations of women globally.